Highway 407 Roadside Safety – Clear Zones and Guiderails

MTO takes matters related to safety seriously.

“Ministry Standards” – comprised of safety standards, specifications, special provisions, directives, codes, policies, best practices, procedures, manuals, guidelines and standard application practices – are always followed. The standards are used throughout the highway lifecycle (i.e., planning, design, construction, operation and maintenance).

One important standard in highway design is the clear zone. A clear zone is an area beyond the travelled lanes to enable a driver to stop safely or regain control of a vehicle that has accidentally left the roadway.

The clear zone width is the distance from the edge of the travelled portion of the roadway to the face of an unprotected object. A slope within the clear zone must be traversable as a minimum. A slope is considered traversable when it is between 1 vertical:4 horizontal and 1 vertical:3 horizontal and is smooth, firm, continuous and free of fixed surface hazards. A vehicle that leaves the road and drives on a traversable slope is typically expected to reach the bottom of the slope without overturning but is not typically expected to be able to recover its regular driving path on the road.

The clear zone width varies from one highway to another depending on the type of roadway or freeway.

The ministry’s desirable standard is to achieve roadside safety through the use of unobstructed clear zones. Guiderail is required in situations where a clear zone is not achievable for reasons such us property constrains or site specific configurations. Guiderail is commonly seen by the public as protection for drivers, however it is a hazard in itself. The ministry’s preference is to eliminate guiderail wherever roadway geometry and property constrains will allow.

Extensive safety analysis has been done for the Highway 407 East Project with the intent of reducing the hazards and roadside barriers within the clear zone of the freeway and all roadways. In highway engineering this is considered to provide an increased level of safety for the drivers. However, in some sections of Highway 407 there is insufficient property width to permit traversable slopes and thus avoidance of the use of guiderail or roadside barriers was not possible.